Spinal implant, driver tool and nut guide

ABSTRACT

A spinal implant for an osteosynthesis device has a vertebral connecting rod for interconnecting adjacent vertebral bodies and comprises an implant body including a head section having a threaded portion, a rod retaining recess opening outward for retaining the connecting rod therein and a slanted engagement surface formed on a bottom wall of the rod retaining recess. The spinal implant further includes a nut member and a rod movement stabilizing device to preserve mobility to the connecting rod.

BACKGROUND OF THE INVENTION

The present invention relates to spinal implants for osteosynthesisdevices and, more particularly, to a spinal implant, a driver toolspecifically suited for the spinal implant, and a nut guide suited forthe spinal implant.

In recent years, various research and development have been attempted toprovide a spinal implant that is designed to achieve adaptation todifferences in alignment, augulation and depth of penetration ofadjacent spinal implants anchored to vertebral bodies which are spacedfrom one another.

One of such implants is disclosed in U.S. Pat. No. 5,154,719. Thisdevice includes a head portion having a pair of upright branches whichare internally threaded and which has a U-shaped recess, and a screwportion projecting from the head portion. A connecting rod is receivedin the two branches, which are fixed in place by means of a ring member.During this operating step, there exist some difficulties in preciselyadjusting the orientation of the U-shaped recesses of the spaced spinalimplants anchored in vertebral bodies, angulation of the spinal implantsand depth of the spinal implants, with a resultant undesirable fixationof the implants and the connecting rod. Since, further, the screwportion is composed of a solid material and the screw portion is merelyanchored in the vertebral body. Accordingly, after the spinal implantpenetrates in the vertebral body, fixation of the spinal implant isunstable and is liable to be undesirably affected with external forceswhen they are applied to the spinal implants.

U.S. Pat. No. 5,879,351 discloses a spinal osteosynthesis devicecomprising at least one vertebral rod, pedicle screws and deformableconnectors. In this prior art, each of the pedicle screws is composed ofthe same solid material as in the prior art discussed above, and adifficulty is similarly encountered in reliably fixing the pedicle screwin the vertebral body. Further, each of the deformable connectors has anoblong opening through which a head portion of the screw extends andeach connector is resiliently supported between a cylindrical base and anut, with a given space being provided for permitting relative movementof the vertebral rod. With such a structure, the spinal implant iscaused to have a large number of component parts, resulting in acomplicated structure and an increased cost.

In known techniques, it has been a usual practice to lock a plug intothe spinal implant by means of a tool holder. In practice, there are twotypes of head section formed with two upright branches, that is, a firsttype of head section having an internally formed thread, and a secondtype of head section having an outwardly formed thread. In the firsttype, the plug is screwed in the internal thread of the head section. Inthis event, the two branches are loosened, thereby providing adifficulty in tightly locking the connecting rod in the spinal implant.On the contrary, in the second type, the plug is screwed onto the outerthread of the head section. In this event, an outer periphery of theplug has a hexagonal profile, and a driver tool having a hexagonalgroove is brought into engagement with the outer hexagonal wall of theplug for rotating the plug. In this event, since the driver tool has anouter diameter larger than that of the plug, increasing an occupyingspace for rotating the driver tool. Under these conditions, when twospinal implants are anchored in adjacent vertebral bodies in arelationship closer to one another, the outer periphery of the drivertool is liable to interfere with the adjacent plug of the spinalimplant, causing difficulties in rotating operation of the driver tool.

SUMMARY OF THE INVENTION

The present invention has been made with a view to overcoming thevarious disadvantages encountered in prior art devices and it istherefore an object of the present invention to provide a spinal implantfor an osteosynthesis device, a driver tool for rotating the spinalimplant, and a nut guide for guiding the implant body and the drivertool.

According to a first aspect of the present invention, there is provideda spinal implant for an osteosynthesis device having a vertebralconnecting rod for interconnecting vertebral bodies spaced from oneanother. The spinal implant comprises an implant body including a headsection having a threaded portion and a rod retaining recess openingoutward for retaining the connecting rod therein, and an anchoring screwsection longitudinally extending from the head section and adapted to bescrewed into the vertebral body, a retaining plug coupled to the headsection of the implant body to maintain the connecting rod in place, androd movement stabilizing means directly located in at least one of therod retaining recess and the retaining plug for allowing pivotalmovement of the connecting rod in the retaining recess, therebypreserving mobility to the connecting rod.

According to a second aspect of the present invention, there is provideda driver tool for a spinal implant having an implant body and ananchoring screw portion, and a nut member screwed onto a head portion ofthe implant body and having an upper wall formed with a tool engagementgroove. The driver tool comprises an elongated shaft, and a tubular toolend having substantially the same diameter as that of the nut member,the tubular tool end having an engaging segment adapted to engage withthe engagement groove formed on the upper wall of the nut member.

According to a third aspect of the present invention, there is provideda nut guide for guiding a nut member of a spinal implant having animplant body and an anchoring screw section, and for guiding a drivertool having a lower end formed with a nut engagement tip, wherein avertebral connecting rod is retained with a pair of the spinal implantto be anchored into vertebral bodies. The nut guide comprises a gripsection, and a hollow cylindrical shaft extending from the grip sectionand adapted to permit insertion of the driver tool therein, thecylindrical shaft having a lower distal end formed with a rod engagingsegment for engaging with and retaining the connecting rod to place thelower distal end in a fixed place, and a threaded bore formed rearwardof the rod engaging segment for momentarily receiving the nut membertherein. The cylindrical shaft allows the driver tool to pass thereinsuch that the nut engagement tip is brought into engagement with the nutmember guided with the cylindrical shaft to move the nut member from thethreaded bore to the implant body of the spinal body.

Other aspect and advantages of the invention will become more apparentfrom the following description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an osteosynthesis device incorporating afirst preferred embodiment of a spinal implant according to the presentinvention, with a connecting rod being utilized to interconnect spacedvertebral bodies by means of plural spinal implants;

FIG. 2 is a side view illustrating the relationship between the pluralspinal implants and the associated connecting rod;

FIG. 3 is an enlarged front view of the first preferred embodiment ofthe spinal implant according to the present invention;

FIG. 4 is a cross sectional view of the spinal implant shown in FIG. 3;

FIG. 5 is another cross sectional view of the spinal implant shown inFIG. 3;

FIG. 6 is a left side view of the spinal implant shown in FIG. 3;

FIG. 7 is an enlarged front view of a second preferred embodiment of aspinal implant according to the present invention;

FIG. 8 is an enlarged front view of a third preferred embodiment of aspinal implant according to the present invention, with the connectingrod being shown as being fastened by the spinal implant of the thirdpreferred embodiment;

FIG. 9 is an enlarged, front view of a nut member forming part of thespinal implant shown in FIG. 8;

FIG. 10 is an enlarged, plan view of the nut member shown in FIG. 8;

FIG. 11 is an enlarged, bottom view of the nut member shown in FIG. 8;

FIG. 12 is an enlarged, front view of a driver tool specifically suitedfor use in the nut member shown in FIG. 8;

FIG. 13 is an enlarged view for illustrating the relationship betweenthe spinal implant and a nut guide of a fourth preferred embodimentaccording to the present invention;

FIG. 14 is a side view of the osteosynthesis device shown in FIG. 13;

FIG. 15 is an enlarged, exploded view of the nut guide shown in FIG. 13;and

FIG. 16 is an enlarged side view of the nut guide shown in FIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings and more particularly to FIGS. 1 and 2, aspinal osteosynthesis device, generally designated at 10, is shown asapplied to separate vertebral bodies 12 for interconnecting pluralvertebral bodies 12 in place.

The spinal osteosynthesis device 10 includes an elongated vertebralconnecting rod 14 retained by a pair of spinal implants 16 of a firstpreferred embodiment according to the present invention. Each of thespinal implants 16 penetrates each vertebral body 12 in a manner as willbe discussed below in detail. The connecting rod 14 is made ofmalleable, elastically deformable material having a large elasticcapacity, permitting elastic deformation necessary for adaptation it todifferences in alignment, angulation and depth of penetration of theimplants 16.

Referring now to FIGS. 3 and 4, the spinal implant 16 includes acylindrical implant body 18 for firmly retaining the connecting rod 14in place, and an anchoring screw section 20 that longitudinally extendsfrom the implant body 18 and adapted to be anchored in the vertebralbody 12 (see FIGS. 1 and 2).

The anchoring screw section 20 has a hollow internal fusion chamber 22,and a plurality of spinal openings 24 each of which is composed of alongitudinally extending elongated slit. Each of the elongated slit 24transversely extends through the anchoring screw section 20 from oneside to the other side and communicates with the internal fusion chamber22 to permit borne ingrowth into the fusion chamber 22. Thus, theanchoring screw section 20 has a plurality of circumferentially spaced,elongated wall segments 26 defined between the hollow internal fusionchamber 22 and the plural slits 24, providing elastic deformation to theanchoring screw section 20 to allow adaptation of any positioning of thethreaded section while permitting an effective fixation withoutimpairing the borne anchorage.

A head portion of the implant body 18 is formed with a U-shaped rodretaining recess 28 that opens outward, and an internally threaded bore30 extending in a longitudinal direction at a position adjacent the rodretaining recess 28. A disc shaped nut member 32 is screwed into theinternally threaded bore 30, thereby retaining the connecting rod 14 inplace in the rod retaining recess 28.

As seen in FIGS. 5 and 6, a bottom wall 34 of the retaining recess 28includes a rod movement stabilizing means 35 composed of slantedengagement surfaces 36 directly located in the rod retaining recess 28for allowing pivotal movement of the connecting rod 14 in the retainingrecess 28, thereby preserving mobility to the connecting rod 14. To thisend, each of the slanted engagement surface 36 is slightly inclined frompoints slightly displaced from the center of axis of the implant body 18at an angle Θ from an axis of the connecting rod 14 perpendicular to theaxis of the implant body 18.

With such a structure, the connecting rod 14 is allowed for pivotalmovement within a range defined by the slanted engagement surfaces 36 ofthe retaining recess 28 of the implant body 18. Thus, the slantedengagement surfaces 36 of the rod movement stabilizing means 35 isdefined in the retaining recess 28 of the implant body 18, allowing theconnecting rod 14 to be inclined.

Although, the connecting rod 14 is inclined in a plane involving thecenter of axis of the implant body 18, the slanted engagement surface 36of the rod movement stabilizing means 35 may be modified such that theconnecting rod 14 is allowed to be slightly inclined in a plane crossingthe central axis of the implant body 18. More particularly, as shown bya phantom line in FIG. 6, the retaining recess 28 has inclinedengagement surfaces 40 formed in a longitudinal direction in right andleft directions in FIG. 6, except for the threaded portion 38.

With the structure discussed above, the plural spinal implants 16 arescrewed into and anchored in separate vertebral bodies 12 in a manner asshown in FIGS. 1 and 2 such that the associated rod retaining sections28 of two implant bodies 18 are aligned, and both ends of the connectingrod 14 are received in the implant bodies 18. In a subsequent step, thenut member 32 are screwed into the threaded portions 30 of the implantbodies 18, respectively, firmly retaining the both ends of theconnecting rod 14 to clamp the same in the required position.

Due to the separate elongated wall segments 26 formed in the anchoringscrew section 20, the anchoring screw section 20 is allowed to bepenetrated into the vertebral body 12 in reduced diametrical size owingto the inward elastic deformation of the separate elongated segments 26,thereby providing ease of penetration of the implant 16. Since, also,when the penetration of the anchoring screw section 20 has beencompleted, the separate elongated wall segments 26 expand to theiroriginal position due to their restoring forces, thereby providing animproved fixation, in an early stage, of the screw section 20 to thevertebral body 12 in a highly reliable manner. Owing to the provision ofthe plurality of spinal openings defined by the elongated slits 24 andthe hollow internal fusion chamber 22, further, the spinal implant 16permits borne ingrowth into the hollow fusion chamber 22 for therebyfurther improving fixation of the implant.

In a event the both ends of the connecting rod 14 are fitted to theretaining recesses 28 of the implant bodies 18 after the plural spinalimplants 16 are firmly fitted to the vertebral bodies 12 in a mannerdiscussed above, if the rotational positions of the retaining recesses28 of the plural spinal implants 16 are not aligned with one another, adesired one of the spinal implants 16 may be slightly rotated. Inaddition, further, when the depths of penetration of the plural spinalimplants 16 are different from one another and the plural spinalimplants 16 undergo misalignment in height, the connecting rod 14 ispartly allowed to be suitably deformed along the slanted surface 36,absorbing a slight difference in height of the bottom walls of theplural spinal implants 16 penetrated in the vertebral bodies 12.

In other words, even when there exists a slight difference in heightbetween the bottom walls 34 of the adjacent spinal implants 16, theconnecting rod 14 is reliably adaptable to that difference, providingimproved engagement of the connecting rod in the plural spinal implantsin an easy and simplified manner.

FIG. 7 shows a second preferred embodiment of a spinal implant accordingto the present invention, with like parts bearing the same referencenumerals as those used in FIGS. 1 to 5.

The spinal implant 16 of FIG. 7 differs in structure from the firstpreferred embodiment of the spinal implant in that the implant body 18has a rod retaining recess 40 composed of a longitudinally extendingoblong opening and a distal end of the implant body 18 has a laterallyextending tool engagement groove 42. The spinal implant 16 of the secondpreferred embodiment has the same advantages as those of the firstpreferred embodiment discussed above. Other features of the secondpreferred embodiment of the spinal implant 16 are identical to those ofthe first preferred embodiment and, accordingly, a detailed descriptionof the second preferred embodiment of the spinal implant 16 is hereinomitted for the sake of simplicity.

FIGS. 8 to 11 show a third preferred embodiment of a spinal implantaccording to the present invention. In FIG. 8, the spinal implant 16includes an implant body 18 and an anchoring screw section 20 having aplurality of small apertures 46 extending in a plane perpendicular tothe axis of the screw portion 20 to allow borne ingrowth therein. Theimplant body 18 has an upper end formed with an outer thread 50, towhich a nut member 52 having an upper wall formed with tool engagementgrooves 56 is screwed. The implant body 18 also has a U-shaped retainingrecess 54, with which a spherical engaging segment 14 a of a connectingrod 14 engages for pivotal movement.

As best seen in FIG. 10, the implant body 18 has a pair of uprightretaining segments 18A, 18B providing relatively large spaces 62 andeach having an arch-shaped cross section. Thus, the upright retainingsegments 18A, 18B provide an open distal end such that when thespherical engaging segment 14A is retained in the U-shaped recess 54,the connecting rod 14 is allowed for pivotal movement relative to thecentral axis of the spinal implant 16.

The nut member 52 has a ring-shape having an inner thread engaging theouter thread 50 of the implant body 18. An upper side of the nut member52 has a plurality of tool engagement grooves 56 that cross each otherin lateral direction. As best seen in FIGS. 9 and 10, the ring-shape nutmember 52 receives therein a central pivot shaft 58 coaxially extendingthrough the nut member 52. A lower ends of the central pivot shaft 58 isintegrally formed with a rod retaining member 60, that includes acentral, globular retaining groove 60 a, and a pair of laterallyextending arch-shaped retaining grooves 60 b. As seen in FIG. 9, the rodretaining member 60 projects downward from a lower distal end of the nutmember 52. The rod retaining member 60 has a radial length substantiallyequal to the diameter of the nut member 52 and has a lateral widthslightly smaller than the width of the rod retaining groove 54. An upperend of the central pivot shaft 58 has a circular flange 58 a havingsubstantially the same shape as the rod retaining member 60.

In FIGS. 8 and 12, there is shown a fourth preferred embodiment of adriver tool 70 for rotating the nut member 52. The driver tool 70includes a hollow, tubular tool end 72 and an elongated shaft 74extending upward from the tubular body 72. A lower end of the tubularbody has a plurality of substantially axially extending engagingsegments 72 a that are adapted to engage with the tool engagementgrooves 56 formed on the upper wall of the nut member 52. The tubularbody 72 is designed to have a diameter substantially equal to the nutmember 52.

With such a structure discussed above, the anchoring screw sections 20of the plural spinal implants 16 penetrates the vertebral bodies and,subsequently, the connecting rod 14 and the spherical engaging segment14 a are located in the rod retaining groove 54 of the implant body 18.In next step, the rod retaining member 60 is brought into engagementwith the rod retaining groove 54 of the implant body 18, and the nutmember 52 is screwed into the outer thread 50 of the implant body 18.The nut member 52 is rotated with the driver tool 70 of which engagingteeth 72 a meshes with the tool engagement grooves 56 of the nut member52, such that the nut member 52 is fixed in place. This movement isenhanced with the aid of the driver tool 70, providing ease of fixingoperation of the nut member 52 to the implant body 18. As previouslydiscussed, since the tubular body 72 has substantially the same diameteras the nut member 52 and an outer periphery of the tubular body 72 ofthe driver tool 70 does not interfere with an outer periphery of theadjacent retaining plug, thereby enhancing easy fixing operations of thedriver tool 70 with respect to the adjacent retaining plugs located in anarrow space. The tool engagement grooves 56 may not be limited to thespecific groove shown in FIGS. 8 and 9, but may have any otherconfiguration such as a bore.

FIGS. 13 to 16 show a fifth preferred embodiment of a driver toolaccording to the present invention, with the spinal implant 16 beingidentical in structure with that of the first preferred embodimentexcept that the retaining plug 32 has a non-circular, hexagonalengagement groove 32A. In the fifth preferred embodiment, an upper endof a driver tool 78 has a grip section 78 a, and a lower portion formedwith a tool end 78 b that has a hexagonal, nut engagement tip 78 c. Thedriver tool 78 is used in combination with a nut guide 80 that includesa grip section 84 and a hollow, cylindrical shaft 82. The grip section84 has an inner guide bore 84 a that is adapted to receive the gripsection 78 a of the driver tool 78. The cylindrical shaft 82 has anaxially extending through-bore 86 to guide the driver tool 78. A lowerend of the cylindrical shaft 82 has an inner threaded bore 88, a nutguide chamber 90, an engaging guide chamber 92, and a rod engagingrecess 94 that is adapted to receive the connecting rod 14. Pluralpreliminary mounting stems 98 are fixedly connected to a mounting base96 for temporarily supporting respective nut members 32 on top ends ofthe stems. The nut members 32 have the hexagonal engagement grooves 32a, respectively.

In operation, the plural spinal implants 16 are sequentially fixed intothe vertebral bodies 12, and the connecting rod 14 is suitably locatedin the rod retaining recesses 28 of the implant 16. In a subsequentstep, the nut guide 80 is placed on one of the nut members 32,which hasbeen placed on the mounting stem 98, such that the nut member 32 isguided through the nut guide hole 90 of the nut guide 80. The nut member32 is thud held with the nut guide 80, and the nut guide 80 is moved toan operating position shown in FIG. 13. In this event, the rod engagingrecess 94 of the nut guide 80 is aligned with the connecting rod 14 suchthat the upper portion of the implant body 18 engages with the engagingguide bore 92 of the nut guide 80 in a manner as shown in FIG. 13. Then,the driver tool 78 is inserted through the nut guide 80 until theengagement tip 78 c engages with the tool engagement groove 32 a of thenut member 32, and the driver tool 78 is rotated to cause the nut member32 to be screwed into the implant body 18 of the spinal implant 16 untilthe nut member 32 is brought into contact with the connecting rod 14.Accordingly, the nut member 32 is easily secured to the implant body 18in a highly reliable manner without causing any misalignments ordifficulties.

The spinal implant, the driver tool and the nut guide of the presentinvention provide numerous advantages over the prior art practices andwhich include:

(A) The spinal implant includes an implant body for retaining avertebral connecting rod, and an anchoring screw section longitudinallyextending from the implant body and adapted to be anchored in avertebral body. The anchoring screw section has a plurality of spinalopenings to permit borne ingrowth therein, with a resultant improvedfixation of the spinal implant. Each of the spinal openings includes alongitudinally extending slit or laterally extending bore thatthoroughly extends from one side to the other side.

(B) The anchoring thread section may also have a hollow, internal fusionchamber communicating with the spinal openings and longitudinallyextending through the thread section to allow borne ingrowth therein.With this structure, the spinal implant can be anchored in the vertebralbody with a suitable fixing condition in an early stage and, in asubsequent stage, the spinal implant can further be firmly anchored inthe vertebral body owing to the borne ingrowth progressed in the spinalopenings and the internal fusion chamber. This results in a reliablefixation of the spinal implant relative to the vertebral body for anextended time period.

(C) A head portion of the implant body has a rod member stabilizingmeans to retain the connecting rod relative to the adjacent spinalimplants for adapting it to the differences in alignment between a rodretaining section and the connecting rod, the height of the rodretaining section, and angulation and depth of penetration of theanchoring screw sections. Thus, the connecting rod can be easilysupported in place with the adjacent spinal implants without causing anycomplicated, troublesome alignments or adjustments of angulation anddepth of penetration of the anchoring screw sections.

(D) The spinal implant also includes a nut member which is designed tobe screwed into a head portion of the implant body, with the nut memberincluding a rod retaining member for retaining the connecting rod inplace in the implant body while permitting pivotal movement of theconnecting rod, thereby preserving smooth mobility to compensate forpositional misalignments or erroneous orientation between the adjacentspinal implants.

(E) A driver tool is employed to rotate the nut member relative to theimplant body, with the driver tool having at least one engaging segmentthat engages with an engagement groove of the nut member and havingsubstantially the same diameter as that of the nut member, enabling thedriver tool to drive the nut member of one of the spinal implants in aneasy manner without conflicting the adjacent nut member of the otherspinal implant closely positioned to the former spinal implant.

(F) A nut guide is proposed for reliably guiding the nut member to beeasily removed to the anchored spinal implant in a highly reliablemanner, and a driver tool is also guided by the nut guide to cause anengaging tip of the driver tool to precisely engage with the engaginggroove of the nut member of the spinal implant. Consequently, the nutmember can be smoothly coupled to the implant body within a short timeperiod without causing rotation of the implant body relative to thevertebral body.

The foregoing description of the preferred embodiments of the inventionhas been presented to illustrate the principles of the invention and notto limit the invention to the particular embodiments illustrated. Forexample, although the preferred embodiments have been illustrated anddescribed that the anchoring screw section of the spinal implantincludes a spinal opening composed of an elongated slip or plurallaterally extending bores, the spinal opening may have any othersuitable configurations such as an oblong opening or an elliptical bore.It is intended that the scope of the invention be defined by all of theembodiments encompassed within the following claims, and equivalentsthereof.

What is claimed is:
 1. A spinal implant for an osteosynthesis devicehaving a vertebral connecting rod for interconnecting adjacent vertebralbodies, comprising: an implant body including a head section having athreaded portion and a rod retaining recess opening outward forretaining the connecting rod therein and a slanted engagement surfaceformed on a bottom wall of the rod retaining recess therein, and ananchoring screw section longitudinally extending from the head sectionand adapted to be screwed into the vertebral body; a nut member screwedto the threaded portion of the head section to maintain the connectingrod in place; and a rod movement stabilizing device directly located inat least one of the rod retaining recess and the nut member for allowingpivotal movement of the connecting rod in the retaining recess, therebypreserving mobility to the connecting rod.
 2. A spinal implant accordingto claim 1, wherein the anchoring screw section has a plurality ofspinal openings to permit borne ingrowth therein.
 3. A spinal implantaccording to claim 2, wherein the anchoring screw section also has ahollow internal fusion chamber formed in an axial direction of thethread section and communicating with the spinal openings to permitborne ingrowth into the spinal chamber.
 4. A spinal implant according toclaim 2, wherein the spinal opening is formed in an elongated slitaxially extending along an axis of the thread section.
 5. A spinalimplant according to claim 2, wherein the rod retaining recess has aU-shaped profile having a semicircular bottom wall, and wherein the rodmovement stabilizing device includes the slanted engagement surfaceformed on the bottom wall of the rod retaining recess to permit pivotalmovement of the connecting rod therein.
 6. A spinal implant according toclaim 4, wherein the anchoring screw section has a plurality oflongitudinally extending thin wall portion to permit plastic deformationof the anchoring screw section.
 7. A spinal implant according to claim2, wherein the spinal openings are formed along the axis of theanchoring screw section in transverse direction thereof.
 8. A spinalimplant according to claim 1, wherein the head section has a threadedportion in close proximity to the retaining recess wherein the nutmember is screwed onto the threaded portion of the head section, the nutmember has an upper wall formed with a tool engagement groove adapted toengage with a driver tool.
 9. A spinal implant according to claim 8,wherein the tool engagement groove includes a transverse groovelaterally formed on the distal end of the nut member.
 10. A spinalimplant according to claim 9, wherein the connecting rod has a sphericalengaging member adapted to be received in the retaining recess of thehead section, with the spherical engaging member being retained in placewith the nut member.
 11. A spinal implant according to claim 10, whereinthe head section includes a pair of arch-shaped upright segments adaptedto engage with first parts of the spherical member, and the nut memberincludes a ring-shaped structure having a pair of arch-shaped engagementgroove adapted to engage with second parts of the spherical member suchthat the head section of the implant body and the nut member permitpivotal movement of the spherical member, thereby preserving mobility tothe connecting rod.